Fe–TiO 2 composite beads driven hybrid process of photocatalysis and photo-Fenton for the degradation of isoproturon

Abstract

The concept of hybrid process of photo-Fenton and photocatalysis, particularly in the fixed mode, has been presented in this study for the degradation of the pesticide isoproturon with reduction at the time of treatment. For fixed-bed studies, spherical beads were prepared by combining definite proportions of clay, foundry sand, and fly ash, which were utilized as iron sources for titanium dioxide (TiO2) immobilization. The optimization of various parameters was performed by utilizing the Box–Behnken design model under response surface methodology. The process of degradation followed first-order kinetics under an optimized condition for the integrated degradation of isoproturon with a 700 mg·L-1 dose of H2O2, 42 spherical beads, and 190 mL of solution for a duration of 176 min at pH 3.7. Approximately 80.96% degradation of isoproturon was observed after inducing the optimized conditions. The integrated treatment was also carried out in a solar batch reactor under optimized conditions to expand its application to industries for treating bio-recalcitrant compounds. The mineralization of isoproturon was confirmed through the generation of nitrate, nitrite, and ammonical nitrogen with a definite chemical oxygen demand reduction. The recyclability of the catalyst was confirmed by recycling the spherical beads characterized by scanning electron microscopy–energy dispersive X-Ray analysis. For confirming the dual effect, that is, the presence of TiO2 along with Fe on the bead’s surface, various analyses including UV–diffuse reflectance spectroscopy, scanning electron microscopy–energy-dispersive spectroscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy were carried out. A tentative pathway for isoproturon removal was also predicted based on intermediate analysis through gas chromatography–mass spectroscopy.